Vacuum-type converter



W. T. BIRDSALL.

VACUUM TYPE CONVERTER.

APPLICATION FILED JAN.5, 1911.

Patented Aug. 23, 1921.

Miami INVENTOR Z0 Mfi/fmd TBImsq/f.

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WITNESSES:

TORNEY umup sir-:

PAriai-Nr orrics.

' wmm .l. BIBDSALL, OF KONTGLAIB. NEW JERSEY, ASSIGNOB. BY ASSIGN- KEH'IS, TO WESTINGHOUSE-LAD comm. A CORPORATION 0;! PENNSYLVANIA.

- Specification of Letters Patent.

YAC'UUI-TYPE CURVE-BT33.

Application filed January 5, 1917. Serial 80. 140,740.

a citizen of the United States, and a resident of Montclair, in the county of Essex and State of New Jersey, have invented a new and useful Improvement in Vacuum-Type @Converters, of which the following is a specification. V

My invention relates 'to vacuum-type electric apparatus of the character wherein the discharge is maintainedby virtue of electron emission, and it has for its object to provide apparatus of the character designated which shall operate eflectively in the absence of auxiliary means for maintainlng one or more electrodes at an electron-emitt1ng temperature.

Another object of my invention is to pro-.

vide apparatus of the character designated:

which shall operate, with stability and effi- -ciency, as a lamp, as a converter, or in other v fields of applicationof apparatus of the general character indicated.

In the accompanying drawmg, Figure 1 1s a side" view, partially diagrammatic, of a;

piece of vacuum-type electric apparatus em bodying one form of my invention, and Figs. 2 and 3 are simllar vlews of modifications ofthe apparatus shown in Fig. 1.

produced and maintained through a highly evacuated spaceby placing therein an anode and a cathode and by maintaining said cathode at" a high temperature. The hot cathode produces electronic emission andthe electrons travel to the anode, permitting current flow in the opposite direction. 7 It has been customary, in the past, .to pro vide a cathode in the form of a filament and to pass auxiliary heating current through said filament-to rendersaid cathode an electron source. This type of apparatus is illustrated in the well known Fleming rectifier and in the De Forest audion, both widely used in wireless telegraphy and telephony.

It is-obviously troublesome and expensive to maintain an auxiliary current source for supplying heating current to the cathode and I have found that, by properly designing a cathode with respect to'its heat-dissipating properties, sufficient heat may be derived from the main current flow, when once initiated, to maintain the cathode there.-

of the character just-described, for operation is continuous, but I also find that operation is possible upon alternating current, where Patented Aug. 23, 1 921.

the heating cfiect of the main discharge is discontinuous. In apparatus of this character, two similar electrodes may be provided, said electrodes being connected, respectively, to the terminals of the alternating-current source and each being preferably provided with auxiliary heating means. lVitlr this form of apparatus, both electrodes are raised to an electron-emitting temperature, whereupon bilateral current flow takes place therebetween, and discontinuous heating effects are produced at both electrodes,.each electrode functioning alternately as an anode and as a cathode. The heat-dissipating properties of each electrode are so adjusted that the heat is conserved during periods of deficiency in the heating effect of the main discharge, thus maintaining each electrode at all times, during operation, at an electron- (mitting temperature.

In all forms of vacuum-electric apparatus, there is a tendency for the discharge to localize upon restricted portions of the elec trode area, producing excessive heating Itis well known that current fiow may be charge similar to that of the associated electrode. In this way, an electrostatic effect is produced upon the discharge, causing it to spread out more. or less uniformly over the entire surface of the electrode. At the same time, the relatively low temperature of said shielding members prevents them from becoming centers of electron emission and, therefore, prevents the flow of the discharge thereto.

Other forms and hases of operation of my invention will ereinafter more fully ap ear.

eferring to Fig. 1 of the drawing for a more detailed understanding of my. invention, I show a highly evacuated container composed of glass or any other suitable material at 7. Said container is provided with two electrodes 8 and 9, each of which is shown as a coiled filament, although, in this y 18 and a switch 19.

particular case, one of said electrodes may take the form of a tungsten or carbon body, as is usual in vacuum-converter practice. The filamentary electrode 8 is mounted between two leading-in wires 10 and 11, and a source of heating current, such, for example, as a battery 12, is connected between said leading-in wires through an adjustable resistor 13 and a switch 14.

In like manner, the filamentary electrode 9 is mounted between leading-in wires 15 and 16 and may be provided with heating current from a source 17 through a resistor A main source of direct current, such, for example, as a battery 20, is connected between the leading-in wires 10 and 15 through a suitable switch 21.

The leading-in wires 10, 11, 15 and 16 are each extended a short distance beyond the associated electrodes, as Shown at 22-22, for a purpose to be hereinafter more fully pointed out.

Having thus described the arrangement of apparatus embodying my invention, the op eration is as follows: At the outset, the switches 14 and 19 are both closed and the resistors 13 and 18 are adjusted to bring the electrodes 8 and 9 to a suitable electr0nemitting temperature. The switch 21 is then closed, permitting current flow from the electrode 9, as an anode. to the electrode 8, as a cathode. The switches 11 and 19 may now be opened, whereupon the electrode 8 continues to function as a source of electronemission, the temperature thereof being maintained by said current flow and the current flow, in turn. depending upon the electron emission. The tendency of the discharge to localize upon restricted portions of the electrodes 8 and 9 is largely eliminated by the electrostatic influence of the shielding horns 2222. Said horns remain comparatively cool because of their relatively large radiating surface, preventing the flow of electrons therefrom and the consequent flow of current thereto. portions of the electrodes 8 and 9, on the other hand, are centrally disposed within the container and have relatively poor heatdissipating properties, thus enabling such electrode portions to maintain a high temperature and an electron-emitting state. Operation may now be continued indefinitely without further use of the auxiliary heating sources 12 and 17. Referring to the form of apparatus shown in Fig. 2, a container 7, similar to that shown in Fig. 1, is provided with similar anodes 8 and 9 mounted be tween leading-in wires 1011 and 15-16. The energy for the operation of the device is derived from a source of alternating current, however, such, for example, as the secondary winding 23 of a transformer 24, the terminals of said secondary winding being connected respectively to the leading-in The main wires 11 and 16. The remaining leading-in wires 10 and 15 may be connected together through a resistor 25 and a switch 26.

To start the device of Fig. 2, the switch 26 is first closed, whereupon alternating current traverses the filaments 8 and 9 and the resister 25, rapidly raising said filaments to an electron-emittingtemperature. The switch 26 is now opened, whereupon a bilateral discharge takes place between the electrodes 8 and 9, the heat generated in each electrode during its periods of anodic activity, combined with that generated during its periods of cathodic activity, being sufiicient to maintain an electron-emitting temperature over the periodic intervals of deficiency in the heating effect of the alternating current.

Both of the above described figures embody apparatus of bilateral conductivity particularly adapted for electric lighting but, obviously, my invention is susceptible of application in connection with converting or rectifying apparatus either of the half wave or single-anode type wherein the cathode must maintain its temperature during intervening half waves or of the full wave or double-anode type wherein the cathode must maintain its temperature only at such times as the back electromotive force of the load and of the converting arc exceeds the instantaneous electromotive force of the alternating-current supply.

Apparatus of the latter type is indicated in Fig. 3 comprising a central condensing chamber 28 provided with laterally and outwardly extending arms 29 and 30. Anodes 31 and 32 of any suitable type, such, for example, as flat disks of refractory material are mounted in the upper portions of the arms 29 and 30, respectively, and are connected to a supply winding 23. A cathode 33 of the hot filament type. is mounted in the lower portion of the chamber 28 and may be raised to an electron-emitting temperature by current from an auxiliary bat tery 20 through a switch 21. The cathode is connected to the mid point of the supply winding 23 through a suitable load 34. In operation, the switch 21 is first closed, causing heating current to ,flow through the cathode 33 and raising the same to an electron-emitting temperature. Load current flows from the anodes 31 and 32 alternately and flows to the cathode before the substantially pure electron stream. The switch 21 may now be opened and the rapidly recurring impulses of load current flowing to the cathode 33 maintain it at such a temperature that sufiicient electrons are continuously given off thereby.

While I have shown my invention in a plurality of different forms, it will be obvious to those skilled in the art that it is susceptible of various other modifications without departingfrom the spirit thereof and'I desire, therefore, that only such limitations shall be placed thereupon as are imposed by theprior art or as are set forth in the appended claims.

I claim as my invention:

1. In an electron tube, the combination with two leading-in Wires, of a filamentary cathode mounted therebetween, means for supplying current to said cathode for the production of electron emission thereat, an

anode mounted within said tube, said leadmeans for maintaining an electromotive force between said cathode and said anode, said leading-in wire extensions being mounted in such relation to said cathode and having such conducting properties as to fail to become the seats of active electron emission.

2. In vacuum-type electric apparatus, the combination with two filamentary electrodes, of means for connecting a source of alternating-current thereto, means for initially passing heating current through each of said electrodes to produce an electron-emitting temperature therein, whereby bilateral current flow is established therebetween, the heat-dissipating properties of said electrodes being so adjusted that they are thereafter maintained at an electron-emitting c temperature solely by said bilateral current flow, and means for substantially preventing the localization of said discharge upon restricted portions of the surface of either of said electrodes.

3. In vacuum-type electric apparatus, the combination with two filamentary electrodes,

of means for connecting a source of alterber, 1916.

WILFRED T. BIRDSALL. 

